The Mole Concept (College Board AP® Chemistry)
Study Guide
Written by: Fallon
Reviewed by: Stewart Hird
The Mole Concept
The number of particles that react in a chemical experiment cannot be directly determined because the size and mass of an individual particle is so small
Moles are used to relate the mass of a sample to the number of particles it contains
The mole (mol) is the SI unit for the amount of substance
The number of moles (n) of a substance and the number of constituent particles or formula units it contains are related by Avogadro’s number (NA)
NA = 6.022 x 1023 mol-1
Number of constituent particles = NA x n
1 mole of… | Fe atoms | H2O molecules | Al2(SO4)3 formula units |
Contains… | 6.022 x 1023 Fe atoms | 1.2044 x 1024 H atoms 6.022 x 1023 O atoms | 1.2044 x 1024 Al3+ ions 1.8066 x 1024 SO42- ions |
Examiner Tips and Tricks
Note that some textbooks will use the terms Avogadro’s constant and Avogadro’s number interchangeably.
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